linux-kernel - Re: [PATCH v7 2/2] trigger: ledtrig-tty: add additional modes

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Message-ID: <20230306093524.amm7o4ppa7gon4ew@pengutronix.de>
Date:   Mon, 6 Mar 2023 10:35:24 +0100
From:   Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
To:     Florian Eckert <fe@....tdt.de>
Cc:     gregkh@...uxfoundation.org, jirislaby@...nel.org, pavel@....cz,
        lee@...nel.org, linux-kernel@...r.kernel.org,
        linux-leds@...r.kernel.org, Eckert.Florian@...glemail.com
Subject: Re: [PATCH v7 2/2] trigger: ledtrig-tty: add additional modes

On Wed, Feb 22, 2023 at 09:33:35AM +0100, Florian Eckert wrote:
> Add additional modes to trigger the selected LED.
> The following modes are supported:
> 
> Tx/Rx:	Flash LED on data transmission (default)
> CTS:	DCE Ready to accept data from the DTE.
> DSR:	DCE is ready to receive and send data.
> CAR:	DCE is receiving a carrier from a remote DTE.
> RNG:	DCE has detected an incoming ring signal.
> 
> The mode can be changed for example with the following command:
> echo "CTS" > /sys/class/leds/<led>/mode
> 
> This would turn on the LED, when the DTE(modem) signals the DCE that it
> is ready to accept data.
> 
> Signed-off-by: Florian Eckert <fe@....tdt.de>
> ---
>  .../ABI/testing/sysfs-class-led-trigger-tty   |  17 ++
>  drivers/leds/trigger/ledtrig-tty.c            | 145 ++++++++++++++++--
>  2 files changed, 147 insertions(+), 15 deletions(-)
> 
> diff --git a/Documentation/ABI/testing/sysfs-class-led-trigger-tty b/Documentation/ABI/testing/sysfs-class-led-trigger-tty
> index 2bf6b24e781b..1c28e6c61d19 100644
> --- a/Documentation/ABI/testing/sysfs-class-led-trigger-tty
> +++ b/Documentation/ABI/testing/sysfs-class-led-trigger-tty
> @@ -4,3 +4,20 @@ KernelVersion:	5.10
>  Contact:	linux-leds@...r.kernel.org
>  Description:
>  		Specifies the tty device name of the triggering tty
> +
> +What:		/sys/class/leds/<led>/mode
> +Date:		January 2023
> +KernelVersion:	6.3
> +Description:
> +		Specifies the operating to trigger the LED.
> +		The following operating modes are supported:
> +
> +		* Tx/Rx: Flash LED on data transmission (default)
> +		* CTS:   DCE Ready to accept data from the DTE.
> +		  LED on if line is high.
> +		* DSR:   DCE is ready to receive and send data.
> +		  LED on if line is high.
> +		* CAR:   DCE has detected a carrier from a remote DTE.
> +		  LED on if line is high.
> +		* RNG:   DCE has detected an incoming ring signal.
> +		  LED on if line is high.

Something I (still) don't like about this approach is that you cannot
make the LED flash on TX only (or CAR and DSR). Something like:

	led=/sys/class/leds/<led>/
	echo 1 > $led/TX
	echo 0 > $led/RX
	echo 1 > $led/CAR

would be a more flexible and IMHO nicer interface. (Maybe with improved
file names.)

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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